The present invention relates to image to film transfer. More particularly, the present invention relates to techniques and apparatus for efficient recording of images to film media.
Throughout the years, movie makers have often tried to tell stories involving make-believe creatures, far away places, and fantastic things. To do so, they have often relied on animation techniques to bring the make-believe to “life.” Two of the major paths in animation have traditionally included, drawing-based animation techniques and stop motion animation techniques.
Drawing-based animation techniques were refined in the twentieth century, by movie makers such as Walt Disney and used in movies such as “Snow White and the Seven Dwarfs” (1937) and “Fantasia” (1940). This animation technique typically required artists to hand-draw (or paint) animated images onto a transparent media or cels. After painting, each cel would then be captured or recorded onto film as one or more frames in a movie.
Stop motion-based animation techniques typically required the construction of miniature sets, props, and characters. The filmmakers would construct the sets, add props, and position the miniature characters in a pose. After the animator was happy with how everything was arranged, one or more frames of film would be taken of that specific arrangement. Stop motion animation techniques were developed by movie makers such as Willis O'Brien for movies such as “King Kong” (1933). Subsequently, these techniques were refined by animators such as Ray Harryhausen for movies including “Mighty Joe Young” (1948) and Clash Of The Titans (1981).
With the wide-spread availability of computers in the later part of the twentieth century, animators began to rely upon computers to assist in the animation process. This included using computers to facilitate drawing-based animation, for example, by painting images, by generating in-between images (“tweening”), and the like. This also included using computers to augment stop motion animation techniques. For example, physical models could be represented by virtual models in computer memory, and manipulated.
One of the pioneering companies in the computer-generated animation (CG animation) industry was Pixar. Pixar is more widely known as Pixar Animation Studios, the creators of animated features such as “Toy Story” (1995) and “Toy Story 2” (1999), “A Bugs Life” (1998), “Monsters, Inc.” (2001), “Finding Nemo” (2003), “The Incredibles” (2004), and others. In addition to creating animated features, Pixar developed computing platforms specially designed for CG animation, and CG animation software now known as RenderMan®. By moving to CG animation, Pixar was faced with additional challenges.
One such challenge was how to accurately and effectively transfer CG animation images onto film, as discussed in the pending patent application discussed above. One specific aspect of this process has been how to correctly profile and/or calibrate a film transfer device, such as a laser film recorder, for a given film media or film stock.
Previous techniques for profiling and/or calibrating a film recorder have been used by Pixar. One such technique included first exposing multiple frames of film to different colors of light in the RGB color space in the film recorder. This included exposing each frame of film to a single unique RGB color. Next, once the film was developed, each frame of film was subjected to a spectroscopic analysis to determine a color in XYZ color space. One such method included determining the amount of light transmitted through each frame (i.e. color density) with respect to wavelength of light. Based upon this data, an RGB to XYZ color space mapping for the film recorder could be determined. In practice, this technique has been very time consuming.
As an example of this previous technique, four thousand frames of film were used and spectroscopicaly analyzed to profile a laser film recorder. Initially, a film recorder exposed each unexposed frame of film to a unique combination of {red, green, blue} values (RGB color space) from an available palette, such as frame 1 to {1,0,0}, frame 2 to {2,0,0}, frame 3 to {0,0,15}, . . . frame 4000 to {128, 128, 255}. The inventors of the present invention have noted that the process of recording about four thousand frames of film, although semi-automated, took hours to complete.
Next, each frame was developed and each frame was subjected to a spectroscopic analysis to determine the intensity of light transmitted at different wavelengths of light (XYZ color space). For example, frame 1 was exposed to white light and a portion of that light was transmitted through frame 1. The transmitted light was then projected through a spectral analyzer. In one system, the spectral analyzer included a prism that would disperse the transmitted light into a rainbow pattern. Additionally, the prism was rotatable such that only a specific portion of the rainbow pattern would strike a camera at a time. Accordingly, the system could detect transmissions of frame 1 with respect to wavelength. The inventors of the present invention have noted that the process of scanning four thousand frames of film, again semi-automated, took hours to complete.
Next, based upon the transmissions per wavelength per frame, a profile for the film recorder was determined. In the above-mentioned patent application, this process was described and termed “determining an RGB to XYZ color space mapping” for the film/film recorder.
In practice, the previous technique has been too time consuming to perform regularly. The inventors of the present invention desire to perform the calibration process more frequently than was done before. For example, calibrating a film recorder every week, every day, after filming out one copy of a feature, receiving a new stock of film media, or the like. To have this ability, the calibration time must be dramatically decreased. In the example above, over 1 day was required to profile the film scanner, which would be too long.
The inventors have considered applying technology from the desktop paper scanner/slide scanner market towards the present problem. For example, for a slide or transparency scanner, a light source provides a white light illumination to a target (e.g. slide, transparency), and three or more CCDs on the back side of the target capture the transmissions through the target. The three or more CCDs typically have filters on top of them such as a red, green, or blue gels at specific frequencies. For example, the red filter may peak at 680 nm+−10 nm, the green may peak at 550+−10 nm, and the like. Such systems are typically single light-pass systems.
In another configuration, a light source provides white light, but a red, green, or blue gel is placed between the white light and the target. Accordingly, a red, green, or blue color is applied to the target, and a monochrome CCD detects the transmission. In this configuration, the filters are similar to the above. Using these technologies, transmissions through the target are captured only about the peak RGB frequencies. Such systems are typically three light-pass systems.
Drawbacks to these approaches include that these scanners cannot provide spectroscopic analysis, because only three distinct frequencies of light are sampled. To perform a spectroscopic analysis, the wavelengths of light illuminating the film should be continuous over the spectrum. An example of the drawback is if a first slide has a reddish color density color peak at 680 nm, and if a second slide has a higher density reddish color peak at 700 nm. Using the slide scanner techniques, the first slide would have a bright recorded intensity because the color of the red filter (680+−10 nm) matches the color (680 nm) of the first slide. However, the second slide would have a lower recorded intensity because the color of the red filter (680+−10 nm) does not match the color (700 nm) of the second slide. In contrast, using a spectroscope, the second slide would have higher intensity, because the second slide has a higher density. Because of the narrow range of filters applied with conventional scanners, the densities of the film are not correctly measured. Accordingly, the inventors do not believe that conventional slide or transparency technologies are relevant for the present application.
In light of the above, what is required are methods and apparatus to more quickly and efficiently profile and calibrate a film recorder without the drawbacks discussed above.